Production of metals from pulverulent materials by flash smelting in an electrically heated furnace



ELVAN DER ETAL FROM PULVERULENT MATERIALS BY FLASH Jan. 23, 1968 PRODUCTION OF METALS SMELTING IN AN ELECTRICALLY HEATED FURNACE Filed Jan. 27, 1964 INVENTORS Hans Ivar E/vancler- HTTOHNEYS United States Patent 3,365,185 PRODUCTION OF METALS FRUM PULVERULENT MATERIALS BY FLASH SMELTING IN AN ELEC- TRICALLY HEATED FURNACE Hans Ivar Elvander and Erik Olof Albin Sundstrorn,

Skelleftehamn, Sweden, assignors to Eoliden Almebolag, a joint-stock company limited of Sweden Filed Jan. 27, 1964, Ser. No. 340,395 Claims priority, application Sweden, Jan. 31, 1963, 1,102/ 63 2 Claims. (Cl. 266-34) The present invention relates to the production of metals from finely divided oxidic or sulfidic ores and more especially flotation concentrates or other dressed products, by directly feeding the reactants to a reaction chamber maintained at reaction temperature by electric heating.

For quite natural reasons, the production of metals from the finely divided melting charge with the omission of preparatory agglomeration, roasting or reduction steps is desirable since in this way substantial simplification of the procedure and other advantages are obtained. Several methods based on this basal principle have been developed. A characteristic of those of the methods of said type which are based on some kind of flash smelting resides in the fact that, on one side, the process has been entirely autogenous, i.e., the exothermic heat of reaction has been sufiicient to impart to the reaction products the desired temperature as well as to maintain the reaction chamber at a proper temperature (if necessary by preheating the reactants charged and/or by using reaction gas enriched with oxygen) or, on the other side, the energy demand has been satisfied by the addition of solid, liquid or gaseous fuels.

In other methods not using flash smelting the finely divided material has been melted in smelting-furnaces fired with fuels or heated electrically. Thereafter, the molten charge may have been subjected to an oxidation or reduction treatment in the same reaction vessel or another one connected thereto. The latter methods are accompanied by obvious drawbacks and has not hitherto been used commerically in any appreciable degree.

In flash smelting, however, the heat generated in the reaction between, in one case, sulfidic concentrates and oxidizing gas and, in the other case, between oxidic materials and reduction agents, is not suflicient or in certain cases negative and, therefore, in these cases, unless making provisions for some kind of external heat supply it is not possible in flash smelting according to conventional methods to impart the proper reaction temperature to the reacting products, neither to maintain the temperature of the reaction chamber at the desired level. This has also been effected by additional heating or, in the case of sulfidic materials, by effecting the combustion to such an extent that the metal to be recovered is oxidized under production of heat. The present invention relates to the case in which, for one reason or other, such as when it is desired to maintain the volume of gas leaving the reaction chamber at a low value or when it is desired to attain a heating which is more advantageous from a technical point of view, it is not desirable to compensate the minimum heat demand of the reaction by additional fuel combustion but rather to generate the additional heat required by electric heating. For reasons of construction, however, electrically heated furnaces have a low height of the roof so that, within the restricted space, it is not possible without special precautions to perform the operations of drying, preheating, ignition and reaction within the short period of time at disposal.

Now it has surprisingly proved possible within the relatively restricted space of an electrically heated furnace to perform a production of metals from finely divided oxidic or sulfidic ores by a process which comprises maintaining 3,365,185 Patented Jan. 23, 1968 within the furnace chamber at least one upright vortex created without supporting walls, by injecting reaction gas of high velocity through at least two nozzles disposed within the furnace chamber and directed tangentially with respect to an imaginary horizontal circle, and charging the finely divided ore into said vortex or vortices.

In addition to the great simplification of the process run by the application of the principle referred to above in the production of lead from lead sulfide concentrate, a substantial saving of energy has been obtained. Hitherto the concentrate was sintered under partial roasting of the sulfur to form under heat generation oxy-sulfidic intermediate products. A stoichiometric proportion between remaining sulfur and oxygen contained in the lead sinter was desirable for the purpose in the melting in the electric furnace to obtain lead and an SO -containing gas as end products. In flash smelting according to the novel process the heat which was previously lost in the sintering process is now transferred to the electric furnace and there substitutes part of the electric energy previously required. Furthermore, the electric energy previously required for effecting the sintering operation, i.e. for the operation of blowers and other apparatuses, is gained (approximately .5 megawatt-hours per 2 shifts).

The increased amount of waste gas resulting from the change to flash smelting conveys an increased amount of heat from the furnace which heat, however, is recovered by an increased steam production in a waste heat boiler connected to the smelting furnace.

In the case of oxidic materials intended for the production of iron the invention involves a further advantage because of the possibility of producing the reaction gas within the furnace and from cheap fuels such as coal breeze, peat and brown coal, whereas in conventional practice the reactive gas is produced from coal and coke outside the furnace. The slag formed may be reduced directly bythe introduction of solid or gaseous reducing agents into the furnace. The slag formed from sulfidic ores is refined in a corresponding way. By injecting the gas in a manner to form isolated vortices and charging the ore concentrate therein, the reaction will proceed within the furnace chamber and not for the most part in a layer adjacent to the furnace Wall which is the case for instance in cyclone-smelting. For this reason the method according to the invention involves reduced attacks on the walls. To provide the desired reaction the temperature of the furnace chamber as well as the amount of gas are adapted to the concentrate to be smelted. Obviously the amount of oxygen supply may be controlled, the gas if necessary preheated and the material dried completely or to a suitable moisture content. The number of vortices may be varied in dependence of the desired output, and the injection and charging, respectively, may be effected through the furnace roof or through inlets located at a high level of the furnace walls. The furnace may have a rectangular, square or circular horizontal cross-sectional area. The approved form of electrical heating by means of Stiderbergelectrodes provides a heat generation within the slag bath according to the resistance principle.

The invention will now be illustrated in more detail with reference to the accompanying drawing in which FIGURE 1 is a horizontal view of an electric smelting furnace adapted for flash smelting of lead concentrate according to the invention, FIGURE 2 a cross-sectional view of the furnace along line Il-II in FIGURE 1, and FIG- URE 3 a detail view showing a nozzle device for creating a vortex and feeding lead concentrate into said vortex.

The furnace shown in FIGURES 1 and 2 comprises a rectangular furnace chamber of small height in relation to the horizontal cross-sectional area of the furnace chamber and provided with a number of heating electrodes 1-4, for instance of the Soderberg type. The electrodes extend downwardly into the furnace chamber through cooling boxes 6-9 disposed on the furnace roof 5, said cooling boxes having conduits (not shown) for the supply and withdrawal of cooling water. The basic construction of the furnace is known per se and used in lead-smelting. The novelty of this furnace resides in the provision of a number of nozzle sets arranged within the furnace chamber for the creation of upright tornado-like air vortices. Thus, in FIGURE 1, between the electrodes 1 and 2, 2 and 3, and 3 and 4, respectively, three such sets of nozzles 13, 14-17 and 18-21, respectively, are shown.

The nozzle device shown in FIGURE 3 comprises a vertical blowpipe 22 extending through the furnace roof and terminating below the roof in a bend 23 of a direction such that the jet stream of air is blown tangentially in relation to an imagined horizontal circle between the respective electrodes. In front of the mouth of the blowpipe a charging tube 24 for lead concentrate debo-uches at the roof level. A branch pipe is connected to the charging tube :with one of its branches 25 extending coaxially with the charging tube 24 and the other branch 26 sloping. The end of the branch 25 is covered by a lid 27 which may be removed for inspection purpose. The charging material is introduced through the branch 26.

In flash smelting of lead concentrate an air-concentrate mixture is injected directly into the furnace chamber through the three sets of each four nozzle devices of the type illustrated in FIGURE 3. The furnace is heated by means of the electrodes 1-4 immersed in the slag layer, wherein due to the ohmic resistance of the slag the heat generated is sufficient to maintain the lead contained in the furnace pot in a molten state. The streams of concentrate supplied through the charging tubes 24 are caught by the compressed air injected through the respective nozzles 23 and entrained into the upright vortex which, due to the tangential injection, is formed without the aid of supporting walls.

The embodiment of the invention illustrated in FIG- URES l to 3 has merely been advanced as a suitable example. Thus, it is possible to introduce the lead concentrate into the vortices through the same nozzles through which the air is injected. Another possibility is to provide pairs of opposite air nozzles at the long sides of the furnace to produce upright vortices between the electrodes, and to charge the concentrate through an opening above the centre of each vortex.

The depictured device, suitably modified, may also be used for reduction of oxidic ores, for instance in reduction of iron ore concentrates, wherein the iron ore concentrate is fed into a gas vortex established by injecting hydrogen and/or carbon monoxide containing gases, if necessary admixed with solid reduction agents such as coke breeze. The reducing gas mixture may then be provided by injection of solid or liquid reducing agents with an oxidizing gas, preferably air, if desired enriched with oxygen and if desired preheated. In the reduction operation the iron ore concentrate, if desired admixed with powdered coal, is fed into a gas vortex provided by the injection of the preheated hydrogen and/ or carbon monoxide containing gases.

Having now described the invention, what we claim as new and desire to secure by Letters Patent, is:

1. A reactor for the production of metals from finely divided ores, comprising a rectangular furnace chamber, means for heating the furnace chamber comprising electrodes inserted through the roof and depending into the furnace chamber wherein the electrodes are arranged in at least One row extending lengthwise of said chamber, at least one set of nozzles for charging finely divided ore to be treated into said chamber, means for discharging reduced metal, means for injecting reactants into said chamber comprising at least one set of at least two nozzles each directed tangentially to an imaginary horizontal circle within said chamber and adapted to inject a gas at high velocity, whereby at least one upright detached gas vortex not supported by the walls of the furnace chamber may be established, the sets of nozzles intended for the formation of the upright gas vortices and the nozzles for charging the ore, respectively, being arranged between the electrodes.

2. A reactor as set forth in claim 1 wherein said reactants comprise a reducing agent chosen from the group consisting of hydrogen and carbon monoxide containing gases.

References Cited UNITED STATES PATENTS BENJAMIN HENKIN, Primary Examiner. 

1. A REACTOR FOR THE PRODUCTION OF METALS FROM FINELY DIVIDED ORES, COMPRISING A RECTANGULAR FURNACE CHAMBER, MEANS FOR HEATING THE FURNACE CHAMBER COMPRISING ELECTRODES INSERTED THROUGH THE ROOF AND DEPENDING INTO THE FURNACE CHAMBER WHEREIN THE ELECTRODES ARE ARRANGED IN AT LEAST ONE ROW EXTENDING LENGTHWISE OF SAID CHAMBER, AT LEAST ONE SET OF NOZZLES FOR CHARGING FINELY DIVIDED ORE TO BE TREATED INTO SAID CHAMBER, MEANS FOR DISCHARGING REDUCED METAL, MEANS FOR INJECTING REACTANTS INTO SAID CHAMBER COMPRISING AT LEAST ONE SET OF AT LEAST TWO NOZZLES EACH DIRECTED TANGENTIALLY TO AN IMAGINARY HORIZONTAL CIRCLE 